"People know Sprint for unlimited," Sprint CEO Marcelo Claure said in a release. "We have long been the leader in offering customers unlimited data and that leadership continues today."

Sprint's unlimited plan comes days after Claure said the carrier recognizes customers ravenous hunger for data and that many are fearful of facing carriers' overage charges. Last year, U.S. wireless consumers used 3.23 trillion megabytes of data, Sprint said, citing the Wireless Association's annual survey. That fact in part prompted the new offering, which bests T-Mobile's $80 a month for unlimited talk, text and data, Sprint said, adding industry leaders AT&T Inc. and Verizon Wireless currently don't offer unlimited data plans.

The move comes in surprisingly nimble fashion for Sprint, which generally has been more methodical with its pricing promotions. Recently, the company has been aggressively marketing that its network has improved, hoping to restore Sprint's image which has been tainted as an unreliable carrier.

Sprint also has adopted the motto of being "back in the game," signaling a refocused in direction after it dropped its merger pursuit of its smaller rival, T-Mobile. Frequent Sprint critic T-Mobile CEO John Legere was rumored to be the next leader of Sprint should a deal pass the scrutiny of regulators.

Now that the behind-the-scenes deal is off — for now — T-Mobile and Sprint are engaged in a war for third place. Sprint recently reported that its has about 54.6 million subscribers, whereas T-Mobile has about 50.5 million.

T-Mobile, however, recently topped Sprint's prepaid customer base. T-Mobile has 15.64 million prepaid subscribers whereas Sprint has only 15.19 million such customers. Industry leaders AT&T Inc. and Verizon Wireless reported 11.34 million and 6.04 million prepaid customers respectively. Prepaid subscribers buy minutes and data as needed and therefore are less lucrative than postpaid clients, who pay monthly bills.

Claure and Sprint Chairman Masayoshi Son have both said Sprint's priorities will be stabilizing and building its customer base. To that end, Claure announced Monday during a block party that the carrier would pay off rivals' contract termination fees and offer up to 10 lines, 20 gigabytes of shared data and unlimited talk and text for $100 a month. It also will double competitors' data for smartphones, tablets and other devices, he said, in addition to terminate its "Framily" plan.